The ways in which we approach wellness are changing—reactionary methods are being replaced with preventative measures, medicine is becoming personalized, and consumers are seeking more ways to monitor their day-to-day health. It is no surprise that the market for wearable biosensors has taken off in recent years. However, the sensors of today are limited in data that they collect. These devices rely on decades-old optical- and electrical-based sensors and are largely limited to measuring pulse and tracking movement. While useful for some applications like fitness tracking, this level of detail is simply inadequate to meet the goal of providing truly useful and actionable health information.
Blood is the gold standard for measuring our biochemistry. Our biochemistry gives information about normal biological processes, pathogenic processes, and even pharmacologic responses to a therapeutic intervention. The next generation of wearable devices must be able to continuously measure biochemistry in real-time. However, continuous sampling is a problem for biofluids such as blood, which requires invasive, needle-based draws at discrete time points. However, other biofluids such as sweat, saliva, and tears contain analytes that can be continuously measured non-invasively. These non-invasive sensing mechanisms are limited because certain analytes are present in blood at more physiologically relevant concentrations compared to non-invasively accessible biofluids (e.g., sweat, saliva, and tears).